EMBRYO, SEED AND CARPEL IN THE DATE. 153 



also be added that the tannin in the cells in these zones, is 

 not confined to the cell walls as it is elsewhere in the endo- 



sperm 



■disapp 



them than in the embryo, may be taken to indicate that the 

 tannin here is concerned chiefly with the embryo. 



Digestion of Reserve Cellulose. — As reserve cellulose plays, 

 if any, a very inconsiderable part in the nutrition of the 

 embryo and because it has been studied, first by Sachs, and 

 very carefully by Reiss (1889), both histologically and 



m 



my p 

 embry 



that there is any digestion of reserve cellulose, even during 



may 



On 



the contrary, as I have already pointed out, the process of 

 cell wall thickening proceeds inwardly toward the embryo 

 until the resting condition is entered. One point of dis- 

 agreement, however, as between Sachs and Reiss has been 

 looked into by me, namely, the presence or absence of the 

 optical evidence of the primary membrane in the defini- 

 tive endosperm cells. Sachs says: ". . . die primaren 

 Zellhaute sind leicht als doppelte conturirte Lamellen 

 zwischen den Verdickungschichten zu erkennen" 32 (1862, 

 p. 242). This Reiss denies categorically, thus: "Die 

 .Wande lassen keinerlei Schichtung, auch keine Mittellamelle 



sichtbar hervor." 



observa 



tion is not as easy as Sachs' wording would lead one to 

 expect. While not everywhere visible with equal ease, how- 

 ever, there is no very great difficulty in determining the 

 substantial correctness of his statement. As for the manner 

 of digestion of the reverse cellulose, I am able to verify 



Reiss' account. 



Origin of the Ferments. 



Sachs believed that the digestion of the endosperm in the 

 date is due to a ferment secreted by the endosperm. Were 

 this not so it would be difficult to explain the remarkable 

 ™; r» m A on na that fhfi softening of the endosDerm exactlv cor- 





33 Quoted by Reiss, 



